AbstractThe aim of this work is to figure out the true effects of filler modification in attapulgite (ATP)/epoxy (EP) nanocomposites through comparing the properties of composites containing pristine or modified ATP clay. ATP particles were first pretreated by a silane coupling agent KH550 and cationic surfactant cetyl trimethyl ammonium bromide (CTAB) separately, and then a series of nanocomposites were prepared with varied clay loadings. Fourier transform infrared spectroscopy and thermogravimetric analysis were used to confirm the modification. The wicking experiment showed the compatibility of ATP with EP increased after modification, especially for CTAB‐ATP, which was discovered to exhibit the highest affinitive ratio. Mechanical and thermal properties of the composites were enhanced on the introduction of ATP. Regarding the efficiency of mechanical reinforcement, KH550 was superior to CTAB at lower ATP loadings (<2 wt%), whereas CTAB became relatively more effective at higher loadings. POLYM. COMPOS., 2013. © 2012 Society of Plastics Engineers